The geological timescale

Several geological timescales exist, reflecting the use of differing datasets and methods of interpretation.

The BGS geological timechart is based on The Geologic Time Scale 2012 by F M Gradstein, J G Ogg, M Schmitz and G Ogg (2012), with additions.

The result is a composite geological timechart that will be updated as improved timescales become available.

How does the BGS geological timechart work?

The principal chart shows the Phanerozoic (Cambrian to Quaternary)
timescale. The names of the individual periods are links: each one
leads to a more detailed chart showing the epochs and ages for that
period.

The charts for the individual periods are all drawn to the same
scale.

Where there is insufficient or contradictory data on the dating
of age boundaries, the ages are given an average duration within
the limits of the appropriate epoch boundaries.

These age boundaries appear as dashed lines on the charts. Generally there is one period
per chart except for the Palaeogene/Neogene/Quaternary, Permian/Triassic
and Ordovician/Silurian.